JP2006071998A - Fixing belt, fixing device, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing belt which can shorten a warm-up time as compared to a fixing belt of a resistance heating system and can maintain a stable exothermic characteristic for a long period of time by suppressing the degradation in durability due to the crack etc., of a metal exothermic layer by a mechanical stress as compared to the fixing belt of the conventional electromagnetic induction heating system. <P>SOLUTION: The fixing belt includes the metal exothermic layer generating heat by an eddy current generated when applied with a magnetic field and fixes the unfixed toner image formed on the surface of the recording medium by heating and pressing, wherein a protective layer composed of a heat resistant resin provided on the surface on the side opposite to the side of the metal exothermic layer where the recording medium is located and the metal protective layer provided on the surface on the side of the metal exothermic layer where the recording medium is located are included. In addition, the metal exothermic layer and the metal protective layer satisfy the formula (1): ρ<SB>A</SB>>ρ<SB>B</SB>. In the formula (1), ρ<SB>A</SB>represents the resistivity (Ω cm) of the metal protective layer, and ρ<SB>B</SB>represents the resistivity (Ω cm) of the metal exothermic layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fixing belt for an electromagnetic induction heating type fixing device in a copying machine or a printer using an electrophotographic method, a fixing device using the same, and an image forming apparatus using the fixing device.

  Conventionally, in an image forming apparatus such as an electrophotographic copying machine or a printer, a process for fixing a toner image formed on a recording medium such as paper on the recording medium to form a permanent image is called a fixing process. Yes. Conventionally, methods such as pressure fixing, oven fixing, solvent fixing, and thermal pressure fixing methods are used in the fixing step, but among these methods, heat can be effectively transmitted and unfixed toner images can be strengthened more firmly. Thermal pressure fixing is the most common because it is fixed and relatively safe.

  In the thermal pressure fixing method, a recording medium on which an unfixed toner image is formed is passed through a nip constituted by two heated rolls or belts, and when the nip passes, the recording medium is heated and melted by the rolls or belts. In this method, the unfixed toner image is fixed on the surface of the recording medium by being pressed against the recording medium by the pressure applied to the nip. At this time, in order to transmit heat to the unfixed toner image, the fixing member (roll or belt) is heated by heating means such as a halogen heater.

  As a method of heating the fixing member, for example, when the fixing member is a roll (fixing roll), generally, a method of heating from inside the roll by radiant heat of a halogen heater provided inside the roll has been used. It was. In this method, since heating is performed from the inside of the roll, it takes time to heat the roll surface to be heated to a state where it can be fixed. Therefore, a waiting time has occurred when the user performs copying or printing. Also, in order to shorten the waiting time as much as possible, it has been common practice to keep the surface of the fixing roll heated to a temperature lower than the fixing temperature during standby, but it is also heated when not in use. However, the demand for energy saving such as prevention of global warming in recent years was not satisfied.

  Accordingly, a fixing device using a thin film and a fixed heater has been proposed as a fixing method corresponding to energy saving (see, for example, Patent Documents 1 and 2). As a result of this technological development, a method of heating by using a thin belt as a fixing member and disposing a planar resistance heating element on the inner surface has come to be widely used. Compared to the method of heating from the center of the roll, this method does not require the air layer as a heat insulating layer to be interposed and the core shaft of the roll does not need to be heated compared to the method of heating the roll from the center. The time for fixing can be shortened.

  However, in the above-described fixing method using a belt and a planar resistance heating element, the planar resistance heating element itself, which is a heater, has a heat capacity, and the user feels a waiting time when sufficient fixing is possible. It's difficult to make it shorter than you can. In addition, since it is difficult to achieve uniform temperature in the axial direction of the planar resistance heating element, it cannot be said that sufficient energy saving and high image quality have been achieved.

On the other hand, in recent years, methods for heating a fixing member by an electromagnetic induction heating method have been studied (see, for example, Patent Documents 3 and 4). The heat generation principle of the fixing method using this electromagnetic induction heating method will be described below.
In a fixing device (induction heating fixing device) using an electromagnetic induction heating method, a coil is used in addition to a fixing member and a pressure member. This coil is installed in a position close to the fixing member inside or outside the fixing member, and is electrically connected to a high-frequency power source. In addition, the fixing member having a metal heat generating layer can be induction-heated regardless of the shape, whether it is a roll shape or a belt shape.

Fixing by such a fixing device is performed as follows. First, a high-frequency alternating current is passed through the coil by a high-frequency power source. At this time, a magnetic flux is generated in the coil in a direction perpendicular to the surface on which the coil is wound according to the direction of the current. This magnetic flux crosses the metal heat generating layer of the fixing member installed in the vicinity of the coil, and an eddy current is generated in the metal heat generating layer of the fixing member so as to generate a magnetic field in the direction to cancel the magnetic flux. Since the metal heat generating layer has a resistance value determined by the metal material constituting the layer and the thickness of the layer, the electric energy generated by the generated eddy current is converted into heat energy.
Since the surface of the fixing member is heated by the heat generation of the metal heating layer at this time, when the recording medium on which the unfixed toner image is formed passes through the nip formed by the fixing member and the pressure member, the unfixed toner image is recorded. It is heat-pressed and fixed on the medium.

  In this method, the surface of the fixing member originally intended to be heated can be effectively heated with high thermal efficiency, so that the time until fixing is possible (hereinafter sometimes referred to as “warm-up time”) is limited. There is a possibility that it can be shortened. As described above, in the induction heating fixing device, there are a roll type using a roll as a fixing member and a belt type using a belt, and in any case, a high frequency current is applied to a coil disposed at a position close to the fixing member. By flowing, an induced electromotive force is generated in the metal heat generating layer of the fixing member, and the eddy current flows to heat the fixing member.

When the fixing member is of a roll type, a metal core constituting the roll can be used as the metal heat generating layer, and by selecting a metal core having a material and thickness that can generate eddy current and be heated by the coil. Heating to a fixing temperature is possible. However, in the roll type, since the core is heated, compared to the conventional heating method, since there is no air layer between the surface of the fixing member and the core, it is quick to reach the fixing temperature. However, since rigidity is required for the core metal itself, a thickness of about several mm is required.
As a result, the heat capacity of the metal core that also functions as the metal heating layer is inevitably increased, and it takes time to heat, so the warm-up time cannot be shortened sufficiently.

  On the other hand, when the fixing member is a belt type, a fixing method using a fixing belt having a metal heat generating layer as a base material and a fixing belt having a metal heat generating layer provided on a base material made of a heat resistant resin are used. There is a method. In the case of a fixing belt in which the metal heat generating layer also serves as a base material, a certain degree of strength is required as the base material. Therefore, the thickness of the metal heat generating layer that also serves as a base material needs to be about several tens to 200 μm. For this reason, although it is not as much as a roll type fixing member, the heat capacity of the base material is increased, so that it takes time to heat the surface of the fixing belt.

  In order to form a nip between the pressure member and the fixing belt, a pressing member that applies a pressing force to the nip must be disposed at a position facing the pressure member inside the fixing belt. In many cases, this pressing member forms a nip with a uniform pressure with the pressure member and uses a rubber pad to secure a nip width. However, since the slidability between the rubber pad and the base material made of metal is poor, the pad may be severely deteriorated.

  On the other hand, in the case of a fixing belt of a type in which a metal heating layer is provided on a base material made of a heat-resistant resin, the heat-resistant resin used for the base material is an engineering plastic such as polyimide or polyamideimide, and 200 ° C or higher It has the heat resistance and the strength is more than a certain level. In the case of a fixing belt made of a heat-resistant resin, the strength is secured by the base material made of a heat-resistant resin. Therefore, if the heat generation performance of the metal heat generating layer can be sufficiently secured, the film thickness is reduced. be able to. Therefore, the warm-up time can be shortened as compared with the fixing belt in which the metal heating layer also functions as a base material. Further, since the base material is made of a heat resistant resin, the sliding property with the rubber pad provided on the inner surface of the fixing belt for forming the nip is also good.

  The metal heating layer provided on the base material made of the heat resistant resin needs to be formed with a uniform film thickness on the base material. The film thickness of this metal heating layer cannot be said more generally than the type of metal constituting this layer, but the lower the resistance metal, the thinner it can be, and in addition, the time to reach the fixable temperature. It can be shortened. In general, metals such as gold, silver, copper, and aluminum are often used as materials constituting the metal heating layer.

  Examples of a method for forming these metal thin films on a substrate made of a heat resistant resin include metal thin film forming methods such as plating, vapor deposition, and sputtering. As described above, the metal thin film has an appropriate film thickness depending on the metal species. However, the thinner the film thickness, the less rigid the fixing belt itself and the more flexible it becomes, so it is easier to form an appropriate nip. Therefore, a good fixing image quality can be obtained. Further, the thinner, the lower the heat capacity of the metal heating layer, which has the advantage of shortening the warm-up time. Therefore, when forming the metal heat generating layer, it is necessary to select a low-resistance metal that generates heat sufficiently even if the film thickness is thin, and to form this metal as thinly and uniformly as possible.

However, in the fixing belt in which the above-described metal heating layer is formed on a base material made of a heat resistant resin, the durability of the metal heating layer is currently lacking.
In particular, in order to obtain a good image quality by reducing the heat capacity of the metal heating layer and shortening the warm-up time, and further improving the flexibility of the fixing belt itself, the thinner the metal heating layer, the smaller the film thickness. On the other hand, the strength of the metal heating layer as a film is reduced.

  The fixing member melts the unfixed toner image on the recording medium and at the same time applies pressure to firmly fix the toner image on the recording medium. Therefore, the fixing member is provided with a pressure member (pressure roll, A nip load is applied between the pressure pad and pressure belt. At this time, when the metal heating layer is thin, defects such as cracks and cracks may occur due to the nip load necessary for fixing. Even when the nip load is low, the fixing belt passes through the nip many times and repeatedly receives bending stress, so that the metal heating layer may have defects such as cracks and cracks.

  In such a fixing member, when a defect such as a crack occurs in the metal heat generating layer, the resistance of the metal heat generating layer is increased or the metal heat generating layer is electrically insulated. Will be reduced. Further, if the generated crack does not reach the crack but has a groove-like defect, a locally thin portion is formed, and as a result, abnormal heat is generated in the groove. This abnormal heat generation has caused the release layer covering the surface of the fixing belt to be burnt or melted, and to cause a significant decrease in the durability of the fixing member.

  Therefore, a polyimide resin is used as the heat-resistant resin constituting the substrate, and the substrate is provided with flexibility by controlling the imidization ratio of the polyimide resin during the formation of the substrate. A technique for reducing mechanical stress on the metal heating layer has been proposed (see Patent Document 5).

  However, the mechanical stress that the metal heat generating layer receives depending on the stress at the nip cannot be sufficiently relaxed only by imparting flexibility to the base material, so that the durability deterioration of the metal heat generating layer cannot be sufficiently solved.

JP-A-63-313182 JP-A-4-44074 JP 11-352804 A JP 2000-188177 A JP 2001-341231 A

  An object of the present invention is to solve the above problems. That is, according to the present invention, the warm-up time can be shortened as compared with the resistance heating type fixing belt, and the durability is reduced due to a crack in the metal heating layer due to mechanical stress as compared with the conventional electromagnetic induction heating type fixing belt. It is an object of the present invention to provide a fixing belt that can suppress heat generation and maintain stable heat generation characteristics over a long period of time, a fixing device using the same, and an image forming apparatus using the fixing device.

The above-mentioned subject is achieved by the following present invention. That is, the present invention
<1>
In a fixing belt that includes a metal heating layer that generates heat due to an eddy current generated when a magnetic field is applied, and is fixed by heating and pressing an unfixed toner image formed on the surface of the recording medium.
A protective layer made of a heat-resistant resin provided on the surface of the metal heating layer opposite to the recording medium; and a metal protection provided on the surface of the metal heating layer on the recording medium side. The fixing belt is characterized in that the metal heating layer and the metal protective layer satisfy the following formula (1).
・ Formula (1) ρ _A > ρ _B
[In the formula (1), ρ _A represents the specific resistance (Ω · cm) of the metal protective layer, and ρ _B represents the specific resistance (Ω · cm) of the metal heating layer. ]

<2>
The fixing belt according to <1>, wherein a specific resistance ρ _A of the metal protective layer is twice or more a specific resistance ρ _B of the metal heating layer.

    <3> The fixing belt according to <1> or <2>, wherein the protective layer made of the heat-resistant resin has a thickness in a range of 10 μm to 100 μm.

    <4> The fixing belt according to any one of <1> to <3>, wherein the metal heating layer has a thickness in a range of 3 μm to 20 μm.

    <5> The fixing belt according to any one of <1> to <4>, wherein the metal protective layer has a thickness in a range of 1 μm to 10 μm.

    <6> The fixing belt according to any one of <1> to <5>, wherein the metal heating layer is made of a metal having copper as a main component.

    <7> The fixing belt according to any one of <1> to <6>, wherein the metal protective layer is made of a metal containing nickel as a main component.

    <8> The fixing belt according to any one of <1> to <7>, wherein the protective layer made of the heat resistant resin includes a polyimide resin.

    <9> The release layer according to any one of <1> to <8>, wherein a release layer is provided on a surface of the metal protective layer opposite to the side on which the metal heating layer is provided. It is a fixing belt.

    <10> The fixing belt according to <9>, wherein the release layer includes a fluororesin.

    <11> The fixing belt according to <9>, wherein an elastic layer is provided between the metal protective layer and the release layer.

<12>
A fixing belt including a metal heating layer that generates heat due to an eddy current generated when a magnetic field is applied; a pressing member that contacts the fixing belt to form a nip and rotates; and the pressing member of the fixing belt includes: In a fixing device including a pressing member that presses a surface opposite to the provided side, and an excitation coil that applies a magnetic field to the metal heating layer by flowing an alternating current,
The fixing device is the fixing device according to any one of <1> to <11>.

<13>
An image carrier, charging means for charging the surface of the image carrier, latent image forming means for forming a latent image on the charged surface of the image carrier, and developing the latent image with a developer to form an unfixed toner image An image forming apparatus comprising at least a developing unit that forms a toner image, a transfer unit that transfers the unfixed toner image to a transfer target, and a fixing unit that heat-fixes the unfixed toner image on a recording medium.
An image forming apparatus, wherein the fixing unit is the fixing device according to <12>.

  As described above, according to the present invention, the warm-up time can be shortened as compared with the resistance heating type fixing belt, and the metal heating layer cracks due to mechanical stress compared with the conventional electromagnetic induction heating type fixing belt. It is possible to provide a fixing belt capable of maintaining a stable heat generation characteristic over a long period by suppressing a decrease in durability due to the above, a fixing device using the same, and an image forming apparatus using the fixing device.

<Fixing belt>
The fixing belt of the present invention is a fixing belt that includes a metal heating layer that generates heat due to an eddy current generated when a magnetic field is applied, and fixes an unfixed toner image formed on the surface of a recording medium by heating and pressing. A protective layer made of a heat-resistant resin provided on the surface of the metal heating layer opposite to the recording medium; and a metal provided on the surface of the metal heating layer on the recording medium side. The metal heating layer and the metal protective layer satisfy the following formula (1).
・ Formula (1) ρ _A > ρ _B
In the above formula (1), ρ _A represents the specific resistance (Ω · cm) of the metal protective layer, and ρ _B represents the specific resistance (Ω · cm) of the metal heating layer.

  Therefore, the fixing belt of the present invention can shorten the warm-up time as compared with the resistance heating type fixing belt, and can be more durable than the conventional electromagnetic induction heating type fixing belt due to cracks in the metal heating layer due to mechanical stress. Therefore, stable heat generation characteristics can be maintained over a long period of time.

  The fixing belt of the present invention has a protective layer made of a heat resistant resin on the surface opposite to the side on which the recording medium of the metal heating layer is located (hereinafter sometimes referred to as “base material” or “heat resistant resin protective layer”). Is provided. For this reason, compared to the case where the metal heat generating layer also functions as a base material, the heat generated in the metal heat generating layer due to the heat insulating effect of the base material is directed to the inner surface of the fixing belt (the surface not in contact with the recording medium). Since the loss is reduced, the warm-up time can be further shortened. Furthermore, since sliding resistance with a pressing member such as a rubber pad provided on the inner surface of the fixing belt can be suppressed, damage to the pressing member can be suppressed and its life can be extended.

Furthermore, the fixing belt of the present invention is provided with a metal protective layer on the surface of the metal heating layer on the side where the recording medium is located. For this reason, since the metal heat generating layer relieves mechanical stress due to repeated deformation in the nip due to repeated rotation of the fixing belt by the metal protective layer, the metal heat generating layer can be used over a long period of time. The occurrence of mechanical defects such as cracks is suppressed, and the heat generation characteristics can be stably maintained.
When such a metal protective layer is not provided, the metal heating layer is strongly subjected to tensile or compressive force on both sides, so that mechanical defects such as cracks are likely to occur, and when used over a long period of time. In this case, the electrical characteristics and heat generation characteristics of the metal heat generation layer are deteriorated.

  In addition, since such a metal protective layer replaces the mechanical durability originally required for the metal heat generating layer itself, the fixing belt of the present invention can make the metal heat generating layer thinner than before. it can. For this reason, the heat capacity of the metal heating layer itself can be suppressed, and the warm-up time can be further shortened.

  In addition, a release layer made of a resin material having a low surface energy such as a fluororesin may be provided on the outer surface of the fixing belt (the surface on the side in contact with the recording medium). Compared with a metal material, the thermal conductivity is low and the strength is also inferior. However, in the case where a release layer is provided in the fixing belt of the present invention, the thickness of the release layer is replaced with the thickness of a metal protective layer having higher thermal conductivity and excellent strength, thereby fixing the fixing belt. The overall strength can be improved and the warm-up time can be further shortened.

In the case where the first metal layer and the second metal layer having two different resistances are provided in contact with each other, when a magnetic field is applied to these metal layers, the metal on the lower resistance side An eddy current is generated in the layer, and the metal layer on which the eddy current is generated generates heat.
Therefore, when the thickness of the metal protective layer is t _A (μm) and the thickness of the metal heating layer is t _B (μm), the resistance values ρ _A / t _A and ρ _B / t of the two metal layers _B (Ω) needs to satisfy the following formula (2).
Formula (2) ρ _A / t _A > ρ _B / t _B

However, even if such a relationship is satisfied, if the material constituting the metal heating layer itself is not low resistance, the magnetic field energy applied to the metal heating layer cannot be efficiently converted into heat energy, resulting in energy loss. In the fixing belt of the present invention, it is necessary to satisfy the formula (1) in addition to the above formula (2) at the same time.
When this relationship is not satisfied, no heat is generated even when a magnetic field is applied to the metal heat generating layer, and the metal protective layer functions as a heat generating layer. For this reason, the warm-up time becomes long and the effects of the present invention may not be achieved.

In addition, the specific resistance ρ _A of the metal protective layer needs to exceed 1 times the specific resistance ρ _B of the metal heating layer, is preferably 2 times or more, and more preferably 3 times or more. When the specific resistance ρ _A of the metal protective layer is less than one time the specific resistance ρ _B of the metal heating layer, the warm-up time becomes long and the effect of the present invention is not achieved. In addition, in the case of exceeding 1 time and less than 2 times, the warm-up time can be surely shortened, but there are cases where it is slightly insufficient as compared with the case of exceeding 2 times.
In addition, the specific resistance ρ _A of the metal protective layer is preferably larger than the specific resistance ρ _B of the metal heating layer. However, from a practical viewpoint such as narrowing of material options, the specific resistance ρ _{A of the} metal protective layer is reduced. Is preferably 20 times or less the specific resistance ρ _B of the metal heating layer.
Here, the value of the specific resistance is based on JIS C 2525 “Conductor Resistance and Volume Resistivity Test Method of Metal Resistance Material”, and is a four-terminal 4 using a resistivity meter Loresta GP MPC-T600 manufactured by Dia Instruments. Measured by the probe method.

-Fixing belt configuration-
The fixing belt of the present invention is not particularly limited as long as the heat-resistant resin protective layer (base material), the metal heating layer, and the metal protective layer are provided in this order from the inner surface side to the outer surface side of the fixing belt. It is preferable to provide a release layer on the outer surface side of the metal protective layer in order to prevent the unfixed toner image from sticking to the outer surface of the fixing belt. Further, an elastic layer may be provided between the metal protective layer and the release layer in order to improve the color image quality and improve the black-and-white image formation speed. Below, each layer which comprises the fixing belt of this invention is demonstrated in detail.

[Heat-resistant resin protective layer]
The heat-resistant resin protective layer in the fixing belt of the present invention is provided adjacent to the heat-resistant resin protective layer at the time of fixing when it is repeatedly circumferentially conveyed using the fixing belt of the present invention to an electromagnetic induction heating type fixing device described later. Even when the metal heat generating layer is heated, it is necessary to maintain high strength without deterioration of physical properties. For this reason, the heat-resistant resin protective layer is mainly composed of a heat-resistant resin.
When a metal film is used instead of the heat resistant resin, it is difficult to ensure the slidability between the pressing member that contacts the inner surface of the fixing belt and the metal film. This is because an image cannot be stably formed over the entire area.

  Therefore, by providing a heat-resistant resin protective layer composed of a heat-resistant resin having higher slidability as the protective layer on the side in contact with the pressing member, there is no sliding resistance with the pressing member, and the life of the pressing member is extended. be able to. Moreover, since the heat resistant resin has a heat insulating effect, the heat generated in the metal heat generating layer can be efficiently used without escaping to the pressing member.

  Examples of the heat-resistant resin that can be used include high heat-resistant and high-strength resins such as liquid crystal materials such as polyimide, aromatic polyamide, and thermotropic liquid crystal polymer, among which polyimide is preferable. Further, the heat insulating effect may be further improved by adding a filler having a heat insulating effect to the heat resistant resin or foaming the heat resistant resin.

The preferable thickness of the heat-resistant resin protective layer is preferably in the range of 10 to 100 μm, and preferably in the range of 30 to 80 μm, from the viewpoint of achieving both rigidity and flexibility that enables repeated circumferential conveyance of the fixing belt over a long period of time. Within the range is more preferable.
If the thickness of the heat-resistant resin protective layer is less than 10 μm, the rigidity is weak, and it may become wrinkles during circumferential movement, or cracks may occur at the edge portions at both ends. On the other hand, when the thickness exceeds 100 μm, flexibility may not be ensured, and the heat capacity may increase, so the warm-up time may be long.

[Metal heating layer]
In the fixing belt of the present invention, the metal heat generating layer has a function of generating heat by an eddy current generated in this layer when a magnetic field is applied, and a metal that generates an electromagnetic induction action is used. As such a metal, for example, either single or two or more kinds of alloys such as nickel, iron, copper, gold, silver, aluminum, chromium, tin, and zinc can be selected. Of these, copper, gold, and silver have low specific resistance, so copper, gold, silver, and alloys thereof are preferable, and copper or copper is the main component in terms of cost and workability (50% or more by weight with respect to the main component). And the same applies to the following).

The thickness of the metal heating layer is preferably thin from the viewpoint of heat capacity. However, if the thickness is less than 3 μm, the resistance value becomes high, so that sufficient eddy current is hardly generated and heat generation is insufficient. In some cases, the time becomes longer, or it becomes impossible to heat to a fixable temperature. Further, if the thickness of the metal heating layer exceeds 20 μm, sufficient heat generation can be obtained, but the heat capacity of the metal heating layer itself increases, so that the warm-up time may become longer.
Therefore, the thickness of the metal heating layer is preferably in the range of 3 to 20 μm, and more preferably in the range of 5 to 15 μm. However, the thickness of the metal heating layer needs to be selected so as to satisfy the relationship of the above-described formula (2) in relation to the thickness of the metal protective layer.

[Metal protective layer]
The metal protective layer preferably has a thickness that can secure sufficient strength in order to relieve mechanical stress applied to the metal heat generating layer, suppress defects such as cracks, and protect the metal heat generating layer. For this reason, the film thickness of the metal protective layer is preferably at least 1 μm or more, more preferably 2 μm or more.
If the film thickness is less than 1 μm, the metal heat generating layer cannot be sufficiently protected, and defects such as cracks may occur in the metal heat generating layer, leading to problems such as deterioration of heat generation characteristics. .

  Accordingly, the metal protective layer is preferably thicker from the viewpoint of ensuring the strength, but as the film thickness increases, the heat capacity also increases, resulting in a longer warm-up time. For this reason, it is preferable that the film thickness of a metal protective layer is 10 micrometers or less, and it is more preferable that it is less than 7 micrometers.

In addition, as long as the material which comprises a metal protective layer satisfy | fills the relationship of Formula (1) mentioned above, the metal material illustrated as a material for the metal heating layer mentioned above can be selected, specifically, It is preferable to use nickel, chromium, tin, zinc, or an alloy containing these metals as a main component.
When the metal heating layer is made of copper or an alloy containing copper as a main component, the metal protective layer is preferably made of nickel or an alloy containing nickel as a main component.

[Release layer]
The fixing belt of the present invention is composed mainly of a low surface energy material such as a fluorine-based compound in order to prevent the surface on the side in contact with the recording medium from adhering to a molten unfixed toner image during fixing. It is preferable that it is composed of a release layer.
Examples of the fluorine compound used in the release layer include fluororubber, polytetrafluoroethylene (hereinafter referred to as “PTFE”), perfluoroalkyl vinyl ether copolymer (hereinafter referred to as “PFA”), tetrafluoride, and the like. A fluororesin such as an ethylene hexafluoropropylene copolymer (hereinafter referred to as “FEP”) can be used, but is not particularly limited.

  In addition, the thickness of the release layer is preferably in the range of 10 to 100 μm, and more preferably in the range of 20 to 50 μm. If the thickness of the release layer is less than 10 μm, the release layer may be worn away by repeated rubbing at the edge of the recording medium. On the other hand, when the thickness of the release layer exceeds 100 μm, the surface flexibility is lost, and as a result, the force for crushing the toner works and the granularity of the fixed image may be impaired. In addition, since the heat capacity increases, the warm-up time may become longer.

[Elastic layer]
In the fixing belt of the present invention, an elastic layer may be further provided between the metal protective layer and the release layer. In particular, when forming a color image, it is preferable to provide an elastic layer.
This is because, when forming a color image, it is necessary to fix the color toner images of four colors of black, magenta, yellow, and cyan on the recording medium. That is, by applying a certain amount of heat uniformly to these four color toner images that are laminated, the four colors are sufficiently melted to obtain a clear color image. When a fixing belt without an elastic layer is used, The stacked toner may be crushed. For this reason, since sufficient heat is not applied to the color toner image close to the recording medium (that is, in the laminated lower layer), the color developability of the color image obtained by fixing may be lowered. Because.

  Even in the case of forming a black and white image, it is preferable to provide an elastic layer in order to cope with a particularly high speed. By providing an elastic layer, the elastic layer is deformed in the nip region, and a sufficient nip width can be obtained even with a low load, so that heat can be transferred to the toner image even at high speeds and fixing is possible. Because it becomes.

In addition, as a material which comprises an elastic layer, a well-known elastic material can be used, As such an elastic material, it is preferable to use heat resistant rubbers, such as a silicone rubber and a fluoro rubber, for example.
Examples of such heat-resistant rubber include liquid silicone rubber SE6744 manufactured by Toray Dow Corning Silicone, Viton B-202 manufactured by DuPont Dow elastomers, and the like.

-Manufacturing method of fixing belt-
As a method for producing the fixing belt of the present invention, a known method can be used. In addition, since a metal heat generating layer and a metal protective layer are thin and it is difficult to handle these layers alone, it is preferable to form a metal heat generating layer and a metal protective layer in this order on the heat resistant resin protective layer. Further, if necessary, a release layer or an elastic layer and a release layer can be formed in order on the metal protective layer.

  When a release layer or an elastic layer and a release layer are formed on the metal protective layer by a coating method, the surface of the metal protective layer or the elastic layer is formed before applying these layers. It is preferable to perform pretreatment with an appropriate primer material as necessary. By performing such pretreatment, the adhesion between the layers can be further improved.

When a release layer or an elastic layer and a release layer are laminated on the metal protective layer by a coating method, the release layer or the elastic layer is subjected to a process of heat-treating the coated film. Is formed.
In the heat treatment of such a coating film, when the metal protective layer is composed of an easily oxidizable metal, the surface of the metal protective layer is oxidized and the adhesion with the layer formed on the surface of the metal protective layer is reduced. May end up. In such a case, it is preferable to perform the heat treatment of the coating film in an inert gas (nitrogen gas, argon gas, etc.) atmosphere.

<Fixing device and image forming apparatus>
Next, a fixing device using the fixing belt of the present invention and an image forming apparatus using the fixing device will be described.
-Fixing device-
The fixing belt of the present invention can be used as a fixing belt of a known electromagnetic induction heating type fixing device (electromagnetic induction heating fixing device). Such a fixing device using the fixing belt of the present invention does not deteriorate the heat generation characteristics of the fixing belt even when used for a long period of time, so that a high image quality can be stably obtained and standby power is low. It is energy-saving to finish. The fixing device using the fixing belt of the present invention preferably has the following configuration.

That is, the fixing device of the present invention includes a fixing belt of the present invention including a metal heating layer that generates heat due to an eddy current generated when a magnetic field is applied, and a pressure that rotates in contact with the fixing belt to form a nip. A member, a pressing member that presses the surface of the fixing belt opposite to the side where the pressing member is provided, and an excitation coil that applies a magnetic field to the metal heating layer by flowing an alternating current It is preferable to have.
In the fixing in such a fixing device, a recording medium on which an unfixed toner image is formed is brought into contact with a fixing belt on which the unfixed toner image is heated in a nip formed between the fixing belt and a pressure member. It is made to insert like this. At this time, when the recording medium passes through the nip, the unfixed toner image is pressed in a molten state and fixed on the surface of the recording medium.

Next, a specific example of such a fixing device will be described in detail with reference to the drawings.
FIG. 1 is a schematic sectional view showing an example of an electromagnetic induction heating fixing device using the fixing belt of the present invention. In FIG. 1, reference numeral 10 denotes a fixing belt of the present invention. A pressure member 11 (a pressure roll in this figure) is disposed so as to be in contact with the fixing belt 10, and a nip is formed between the fixing belt 10 and the pressure member 11. The pressing member 11 has a configuration in which an elastic body layer 11b made of silicone rubber or the like is formed on a base material 11a, and a release layer 11c made of a fluorine-based compound is further formed thereon.

  Inside the fixing belt 10, a pressing member 13 that presses the inner surface of the fixing belt 10 and locally increases the nip pressure is provided at a position facing the pressing member 11. The pressing member 13 includes a nip head 13b that contacts the inner surface of the fixing belt 10 and presses the nip, a nip pad 13c made of silicone rubber or the like that holds the nip head 13b, and a support 13a that supports the nip pad 13c. Has been.

Further, an electromagnetic induction heating device 12 including an electromagnetic induction coil (excitation coil) 12a is provided at a position facing the pressing member 11 with the fixing belt 10 as the center. The electromagnetic induction heating device 12 applies an alternating current to the electromagnetic induction coil, thereby changing the generated magnetic field by an excitation circuit and generating an eddy current in the metal heating layer of the fixing belt 10. This eddy current is converted into heat (Joule heat) by the electric resistance of the metal heating layer, and as a result, the surface of the fixing belt 10 generates heat.
The electromagnetic induction heating device 12 may be installed upstream in the rotational direction B with respect to the nip region in the heat fixing belt 10.

Next, fixing by the electromagnetic induction heating fixing device shown in FIG. 1 will be described. First, the pressing member 11 is rotated in the direction of arrow C by a driving device (not shown), and the fixing belt 10 is also rotated in the direction of arrow B accordingly. Here, the recording medium 15 on which the unfixed toner image 14 is formed is inserted in the nip portion of the fixing device in the arrow A direction. At this time, the unfixed toner image 14 is pressed against the surface of the recording medium 15 in a molten state, and is fixed on the surface of the recording medium 15.
In the example shown in FIG. 1, the driving method is belt driving (roll is driven), but roll driving (belt is driven) may be used.

As the fixing belt 10 used in the fixing device shown in FIG. 1, for example, a belt having a configuration as shown in FIG. 2 can be used. FIG. 2 is a schematic cross-sectional view showing a configuration example of the fixing belt of the present invention.
A fixing belt 10 shown in FIG. 2 includes a metal heating layer 10b made of a conductive member that self-heats by electromagnetic induction, a metal protection layer 10c, an elastic layer 10d, and a fluorine-based material on the outer peripheral surface of the heat-resistant resin protection layer 10a. A release layer 10c containing a compound is formed in order.

Next, the heat generation principle of the metal heat generating layer 10b by electromagnetic induction will be described below.
First, when an alternating current is applied to the electromagnetic induction coil 12a by an unillustrated excitation circuit, the magnetic flux repeatedly generates and disappears around the electromagnetic induction coil 12a. When this magnetic flux crosses the metal heating layer 10b of the fixing belt 10, an eddy current is generated in the metal heating layer 10b so as to generate a magnetic field that hinders the change of the magnetic flux. Joule heat is generated by the eddy current and the specific resistance of the metal heating layer 10b.

The eddy current flows almost concentrated on the surface of the metal heating layer 10b on the side of the electromagnetic induction heating device 12 due to the skin effect, and generates heat with electric power proportional to the skin resistance Rs of the metal heating layer 10b. Here, when the angular frequency is ω, the magnetic permeability is μ, and the specific resistance is ρ, the skin depth δ is expressed by the following equation (3).
Formula (3) δ = (2ρ / ωμ) ^1/2

Furthermore, the skin resistance RS is represented by the following formula (4).
Formula (4) Rs = ρ / δ = (ωμρ / 2) ^1/2
The electric power P generated in the metal heat generating layer 10b of the fixing belt 10 is expressed by the following equation, where Ih is the current flowing through the fixing belt 10.
Formula (5) P∝Rs∫ | Ih | 2dS

Therefore, if the skin resistance Rs is increased or the current Ih is increased, the electric power P can be increased and the amount of heat generation can be increased. Here, the skin depth δ (m) is expressed by the following equation (6) by the frequency f (Hz) of the excitation circuit, the relative permeability μr, and the specific resistance ρ (Ω · m).
Formula (6) δ = 503 (ρ / (fμr)) ^1/2

This indicates the depth of absorption of electromagnetic waves used in electromagnetic induction, and the intensity of electromagnetic waves is 1 / e or less deeper than this, and conversely most energy is absorbed to this depth. Yes.
Here, the thickness of the metal heating layer 10b is preferably thicker (3 to 100 μm) than the skin depth represented by the above formula. This is because if the thickness of the metal heating layer 16b is smaller than 3 μm, most of the electromagnetic energy cannot be absorbed and the efficiency may deteriorate.

-Image forming device-
Next, an image forming apparatus using the fixing device of the present invention will be described. The image forming apparatus of the present invention is not particularly limited as long as it uses the fixing device of the present invention as a fixing device in a known image forming apparatus using an electrophotographic method, but has the following configuration. It is preferable.
That is, the image forming apparatus of the present invention includes an image carrier, a charging unit that charges the surface of the image carrier, a latent image forming unit that forms a latent image on the charged surface of the image carrier, and the latent image. Developing means for developing an unfixed toner image by developing with a developer, transfer means for transferring the unfixed toner image to a transfer target, and fixing means for heating and fixing the unfixed toner image on a recording medium (of the present invention) It is preferable to have a configuration including at least a fixing device. Moreover, you may equip other well-known mechanisms and members as needed.

  Such an image forming apparatus according to the present invention does not deteriorate the heat generation characteristics of the fixing belt even when used for a long period of time, so that it is possible to stably obtain high image quality and to save energy because less standby power is required. It is.

Examples of the present invention will be described below. However, the method for producing the fixing belt of the present invention used in the examples is not limited to the following examples.
Example 1
-Fixing belt production-
An endless belt having a film thickness of 60 μm and an outer diameter of 30 mm was produced using polyimide resin (trade name: U Varnish-S, manufactured by Ube Industries) as a heat-resistant resin protective layer. Next, the outer peripheral surface of the endless belt was subjected to alkali etching treatment, washed, and the outer peripheral surface was subjected to electroless copper plating to form a copper layer of 0.5 μm. Next, using this electroless copper plating film as an electrode, a copper layer having a thickness of 10 μm was formed thereon by electrolytic plating. Subsequently, a nickel layer having a thickness of 6 μm was formed on the copper layer by electrolytic plating. Further, a fluororesin (PFA) dispersion paint (trade name: EN-710CL, manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) is applied on the nickel layer, and then left in a furnace at 380 ° C. for 1 hour to obtain a fluororesin. A PFA layer having a film thickness of 30 μm was formed by baking the coating film to obtain a fixing belt.

-Fixing device-
For the evaluation of the fixing belt of Example 1, an electromagnetic induction heating and fixing device having a fixing belt, a pressure roll, an exciting coil (electromagnetic induction coil), and a pressing member for pressing the fixing belt and the pressure roll. Evaluation was carried out by mounting on a fixing device (main part having the configuration shown in FIG. 1). Details of the fixing device will be described below.
The pressing member includes an outer diameter portion that is substantially the same as the inner diameter of the fixing belt, an outer shape portion that is larger than the outer diameter portion, and an edge guide that is fitted into both ends of the fixing belt to restrict movement of the fixing belt in the axial direction. And a folder having a pressure rubber pad mounting portion having a diameter smaller than the inner diameter of the fixing belt, and a pressure rubber pad.

In assembling the fixing device, the pressing member, the fixing belt, and the pressure roll were arranged as follows.
First, after fixing the pressing rubber pad to the pad mounting portion of the folder after inserting the pressing member into the inner peripheral side of the fixing belt, edge guides of the pressing member were attached to both ends of the fixing belt. Subsequently, a part of the outer circumferential surface of the fixing belt provided with the pressing member on the inner peripheral side is brought into contact with the pressure roll, and a load is applied between the pressure roll shaft and the pressing member. The rubber pad of the member and the pressure roll were pressed against each other via a fixing belt to form a nip (in addition to using a pressure belt stretched on two or more shafts or rollers, A nip may be formed by pressing against the fixing belt).
As a material constituting the edge guide and the folder, a resin (PPS or the like) that does not generate an induced electromotive force due to an alternating current and has heat resistance in a fixing temperature region is used.

The exciting coil used in the fixing device is a litz wire in which 16 φ0.5 mm copper wires that are insulated from each other are bundled, and this is longer than the width of the fixing belt and the circumferential length of the fixing belt. In order to make the gap between the exciting coil and the fixing belt uniform, the winding is wound so as to cover 1/6 to 1/4 of that of the fixing belt and has a curvature that follows the curvature of the fixing belt. Formed. The fixing coil was fixed on the outer peripheral surface of the fixing belt so that the gap between the exciting coil and the fixing belt was 2 mm.
At the time of fixing, an alternating current is passed through the exciting coil by an exciting circuit to generate a magnetic field around the exciting coil. Therefore, when the generated magnetic field crosses the metal heating layer of the fixing belt, an eddy current is generated in the metal heating layer that generates a magnetic field in a direction that cancels the magnetic field crossed by electromagnetic induction. Thereby, heat generation according to the eddy current value at this time and the resistance of the metal heating layer is obtained.

The pressure roll is formed by providing a foamed silicone rubber layer having a thickness of 12 mm as an elastic layer on a solid shaft having an outer diameter of 16 mm, and further covering this layer with a PFA tube having a thickness of 30 μm.
Specifically, this pressure roll was produced as follows. First, a fluororesin tube having an outer diameter of 50 mm, a length of 340 mm, and a thickness of 30 μm, in which an adhesive primer was applied to the inner peripheral surface of the PFA tube, and a solid shaft were set in a molding die. Subsequently, after injecting liquid foamed silicone rubber to a thickness of 2 mm between the fluororesin tube and the solid shaft, the rubber layer is vulcanized and foamed by heat treatment (150 ° C. × 2 hrs) to form an elastic layer. The pressure roll was produced by forming.
The pressure roll is connected to a motor via a gear, and the fixing belt is driven by driving the pressure roll to convey the recording medium.

-Evaluation method-
In the evaluation method, the above-described electromagnetic induction heating and fixing apparatus was evaluated by performing a 200,000 sheet passing test using J paper manufactured by Fuji Xerox Co., Ltd.
Evaluation items include heat generation characteristics, warm-up time (however, the fixable temperature to be reached is set to 180 ° C.), temperature distribution in the fixing belt, and power factor of 200,000 sheets, which is an electric characteristic of the fixing belt. It is a change before and after. Here, the power factor is when the phase difference θ between the current and voltage flowing in the exciting coil is measured as a result of the eddy current generated in the metal heating layer provided on the fixing belt when a high frequency current is passed through the exciting coil. Of cos θ. The closer the phase difference θ is to 0, the higher the power factor, and it can be said that the heat generation is more likely.
The specific methods for measuring and evaluating the warm-up time, the temperature distribution in the fixing belt, and the power factor are as follows.

<Warm-up time>
When the electromagnetic induction coil is energized, the surface temperature of the fixing belt is measured with a non-contact infrared radiation thermometer (manufactured by Keyence Corporation), and the time from the start of energization until the surface temperature reaches 180 ° C. is defined as the warm-up time. .

<Temperature distribution in fixing belt>
When the electromagnetic induction coil is energized, the surface temperature of the fixing belt is measured with a non-contact infrared radiation thermometer (manufactured by Keyence Corporation), and the temperature distribution in the surface of the fixing belt when the surface temperature reaches 180 ° C. Detected and evaluated.
In the following description, the temperature distribution in the fixing belt being “uniform” means that the temperature distribution difference (maximum value−minimum value) within the fixing belt surface is within 10 ° C.

<Power factor>
The part other than the exciting coil of the electromagnetic induction device is changed to an impedance meter WT1600FC manufactured by Yokogawa Electric Corporation, and when a high frequency current of 20 KHz is passed through the exciting coil, the phase difference θ between current and voltage is measured, and the power factor (cos θ) Was calculated. The power factor was evaluated by relative evaluation of the power factor after the paper passing when the power factor before the paper passing test was 1.0.

-Evaluation results-
When 200,000 sheets were passed through this electromagnetic induction heating and fixing apparatus using the fixing belt obtained in Example 1, when the power factor before the sheet passing test was 1.0, The power factor was 1.0 with no change. In addition, the warm-up time before and after passing through was 7 seconds, and the temperature distribution after passing through the paper remained uniform.

(Example 2)
A polyimide endless belt having a film thickness of 20 μm and an outer diameter of 30 mm was prepared using a polyimide resin (trade name: U Varnish-S, manufactured by Ube Industries) as a heat-resistant resin protective layer. Next, a copper layer having a thickness of 10 μm was formed on the outer peripheral surface of the endless belt after performing alkali etching treatment and cleaning in the same manner as in Example 1. Subsequently, a nickel layer having a thickness of 2 μm was formed thereon by electrolytic plating. Thereafter, a fluororesin dispersion paint (trade name: EN-710CL, manufactured by Mitsui DuPont Fluoro Chemical Co., Ltd.) was applied on the nickel layer, and baked in an oven at 380 ° C. for 1 hour. The thickness of the fluororesin layer was 30 μm.

  The fixing belt thus prepared was mounted on the electromagnetic induction heating fixing device used in Example 1, and 200,000 sheets were passed through. When the power factor before the sheet passing test was 1.0, the fixing belt was passed through. The post paper power factor was 0.96, almost unchanged. In addition, the warm-up time before and after passing through the paper was 4 seconds, and the temperature distribution after passing through the paper remained uniform.

(Example 3)
A polyimide endless belt having a film thickness of 90 μm and an outer diameter of 30 mm was produced using a polyimide resin (trade name: U Varnish-S, manufactured by Ube Industries) as a heat-resistant resin protective layer. Next, a copper layer having a thickness of 10 μm was formed on the outer peripheral surface of the endless belt after performing alkali etching treatment and cleaning in the same manner as in Example 1. Subsequently, a nickel layer having a thickness of 9 μm was formed thereon by electrolytic plating. Thereafter, a fluororesin dispersion paint (trade name: EN-710CL, manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) was applied onto the nickel layer, and baked in an oven at 380 ° C. for 1 hour. The thickness of the fluororesin layer was 30 μm.

  The fixing belt thus prepared was mounted on the electromagnetic induction heating fixing device used in Example 1, and 200,000 sheets were passed through. When the power factor before the sheet passing test was 1.0, the fixing belt was passed through. The post paper power factor was 1.0, unchanged. In addition, the warm-up time before and after the passage was 9 seconds, and the temperature distribution after the passage remained uniform.

Example 4
A polyimide endless belt having a film thickness of 40 μm and an outer diameter of 30 mm was prepared using a polyimide resin (trade name: U Varnish-S, manufactured by Ube Industries) as a heat-resistant resin protective layer. Next, a copper layer having a thickness of 12 μm was formed on the outer peripheral surface of the endless belt after performing alkali etching treatment and cleaning in the same manner as in Example 1. Subsequently, a nickel layer having a thickness of 4 μm was formed thereon by electrolytic plating. Thereafter, a fluororesin dispersion paint (trade name: EN-710CL, manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) was applied onto the nickel layer, and baked in an oven at 380 ° C. for 1 hour. The thickness of the fluororesin layer was 30 μm.

  The fixing belt thus prepared was mounted on the electromagnetic induction heating fixing device used in Example 1, and 200,000 sheets were passed through. When the power factor before the sheet passing test was 1.0, the fixing belt was passed through. The post paper power factor was 0.98, almost unchanged. In addition, the warm-up time before and after the passage was 6 seconds, and the temperature distribution after the passage remained uniform.

(Example 5)
A polyimide endless belt having a film thickness of 70 μm and an outer diameter of 30 mm was prepared using a polyimide resin (trade name: U Varnish-S, manufactured by Ube Industries) as a heat-resistant resin protective layer. Next, an alkali etching treatment and cleaning were performed on the outer peripheral surface of the endless belt in the same manner as in Example 1, and then a copper layer having a thickness of 8 μm was formed. Subsequently, a nickel layer having a thickness of 7 μm was formed thereon by electrolytic plating. Thereafter, a fluororesin dispersion paint (trade name: EN-710CL, manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) was applied onto the nickel layer, and baked in an oven at 380 ° C. for 1 hour. The thickness of the fluororesin layer was 30 μm.

  The fixing belt thus prepared was mounted on the electromagnetic induction heating fixing device used in Example 1, and 200,000 sheets were passed through. When the power factor before the sheet passing test was 1.0, the fixing belt was passed through. The post paper power factor was 1.0, unchanged. In addition, the warm-up time before and after the passage was 9 seconds, and the temperature distribution after the passage remained uniform.

(Example 6)
A polyimide endless belt having a film thickness of 30 μm and an outer diameter of 30 mm was prepared using a polyimide resin (trade name: U Varnish-S, manufactured by Ube Industries) as a heat-resistant resin protective layer. Next, an alkali etching treatment and cleaning were performed on the outer peripheral surface of the endless belt in the same manner as in Example 1, and then a copper layer having a thickness of 5 μm was formed. Subsequently, a nickel layer having a thickness of 3 μm was formed thereon by electrolytic plating. Thereafter, a fluororesin dispersion paint (trade name: EN-710CL, manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) was applied onto the nickel layer, and baked in an oven at 380 ° C. for 1 hour. The thickness of the fluororesin layer was 30 μm.

  The fixing belt thus prepared was mounted on the electromagnetic induction heating fixing device used in Example 1, and 200,000 sheets were passed through. When the power factor before the sheet passing test was 1.0, the fixing belt was passed through. The post paper power factor was 0.97, almost unchanged. In addition, the warm-up time before and after the passage was 15 seconds, and the temperature distribution after the passage remained uniform.

(Example 7)
A polyimide endless belt having a thickness of 80 μm and an outer diameter of 30 mm was prepared using a polyimide resin (trade name: U Varnish-S, manufactured by Ube Industries) as a heat-resistant resin protective layer. Next, a copper layer having a thickness of 15 μm was formed on the outer peripheral surface of the endless belt after performing alkali etching treatment and cleaning in the same manner as in Example 1. Subsequently, a nickel layer having a thickness of 8 μm was formed thereon by electrolytic plating. Thereafter, a fluororesin dispersion paint (trade name: EN-710CL, manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) was applied onto the nickel layer, and baked in an oven at 380 ° C. for 1 hour. The thickness of the fluororesin layer was 30 μm.

  The fixing belt thus prepared was mounted on the electromagnetic induction heating fixing device used in Example 1, and 200,000 sheets were passed through. When the power factor before the sheet passing test was 1.0, the fixing belt was passed through. The post paper power factor was 1.0, unchanged. In addition, the warm-up time before and after passing through was 10 seconds, and the temperature distribution after passing through the paper remained uniform.

(Example 8)
A polyimide endless belt having a film thickness of 50 μm and an outer diameter of 30 mm was prepared using a polyimide resin (trade name: U Varnish-S, manufactured by Ube Industries) as a heat-resistant resin protective layer. Next, a copper layer having a thickness of 10 μm was formed on the outer peripheral surface of the endless belt after performing alkali etching treatment and cleaning in the same manner as in Example 1. Subsequently, a nickel layer having a thickness of 5 μm was formed thereon by electrolytic plating.
Further, a liquid silicon rubber having a film thickness of 200 μm was applied as an elastic layer via a primer (manufactured by Toray Dow Corning, DY39-111) applied on the nickel layer, and vulcanization was performed. Subsequently, a heat resistant primer (Teflon (registered trademark) primer “855-021 (manufactured by DuPont)” water-based paint) is applied to the surface of the elastic layer, and then a PFA dispersion “500CL (manufactured by DuPont). “Water-based paint” was applied and baked at 380 ° C. to form a release layer having a thickness of 30 μm.

  The fixing belt thus prepared was mounted on the electromagnetic induction heating fixing device used in Example 1, and 200,000 sheets were passed through. When the power factor before the sheet passing test was 1.0, the fixing belt was passed through. The post-paper power factor was 0.99, almost unchanged. In addition, the warm-up time before and after passing through was 10 seconds, and the temperature distribution after passing through the paper remained uniform. In addition, when the image quality of the color image was confirmed, the image quality was good.

(Comparative Example 1)
A polyimide endless belt having a film thickness of 20 μm and an outer diameter of 30 mm was prepared using a polyimide resin (trade name: U Varnish-S, manufactured by Ube Industries) as a heat-resistant resin protective layer. Next, a copper layer having a thickness of 10 μm was formed on the outer peripheral surface of the endless belt after performing alkali etching treatment and cleaning in the same manner as in Example 1. Thereafter, a fluororesin dispersion paint (trade name: EN-710CL, manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) was applied onto the copper layer, and baked in a nitrogen-purged furnace at 380 ° C. for 1 hour. The thickness of the fluororesin layer was 30 μm.

  When the fixing belt thus prepared was mounted on the electromagnetic induction heating fixing device used in Example 1 and a paper passing test was performed, the power factor started to decrease from the time when 80,000 sheets passed, As a result of the insufficient temperature rise and the in-plane temperature difference becoming large, cold offset occurred due to insufficient temperature at the end of the fixing belt after the 110,000th sheet. Finally, a 200,000 sheet passing test was performed. When the power factor before the test was 1.0, the power factor after passing the sheet decreased to 0.70. The warm-up time was 6 seconds before the paper was passed, but it was delayed to 20 seconds after the paper was passed.

(Comparative Example 2)
A copper layer having a film thickness of 10 μm was formed on the outer peripheral surface of a nickel endless belt having a film thickness of 50 μm and an outer diameter of 30 mm produced by electroforming. Subsequently, a nickel layer having a thickness of 6 μm was formed thereon by electrolytic plating. Thereafter, a fluororesin dispersion paint (trade name: EN-710CL, manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) was applied onto the nickel layer, and baked in an oven at 380 ° C. for 1 hour. The thickness of the fluororesin layer was 30 μm.

  The fixing belt manufactured in this manner was mounted on the electromagnetic induction heating fixing device used in Example 1, and a sheet passing test was performed. As a result, after 50,000 sheets passed, the belt was driven by friction with the pressing member. It became worse, and the power supply to the exciting coil stopped due to the operation of the rotation detection function when the number of sheets passed was 60,000. There was no decrease in power factor at this time, and the warm-up time was 9 seconds, but it was not usable.

Example 9
A polyimide endless belt having a film thickness of 5 μm and an outer diameter of 30 mm was prepared using a polyimide resin (trade name: U Varnish-S, manufactured by Ube Industries) as a heat-resistant resin protective layer. Next, a copper layer having a thickness of 10 μm was formed on the outer peripheral surface of the endless belt after performing alkali etching treatment and cleaning in the same manner as in Example 1. Subsequently, a nickel layer having a thickness of 6 μm was formed thereon by electrolytic plating. Thereafter, a fluororesin dispersion paint (trade name: EN-710CL, manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) was applied onto the nickel layer, and baked in an oven at 380 ° C. for 1 hour. The thickness of the fluororesin layer was 30 μm.

The fixing belt thus prepared was mounted on the electromagnetic induction heating fixing device used in Example 1, and a paper passing test was performed. As a result, the edge guide (the movement of the fixing belt in the axial direction was restricted by 110,000 sheets). The end of the fixing belt was bent due to contact with the member.
The bending of the end portion was due to the strength of the fixing belt being insufficient, but it was found that it can withstand up to 110,000 sheets and has sufficient durability in practical use.
The warm-up time before passing through and after 110,000 sheets was 4 seconds and 4 seconds, respectively, the power factor was 1.0 and 0.96, respectively, and the temperature distribution was also uniform.

(Example 10)
A polyimide endless belt having a film thickness of 120 μm and an outer diameter of 30 mm was prepared using a polyimide resin (trade name: U Varnish-S, manufactured by Ube Industries) as a heat-resistant resin protective layer. Next, a copper layer having a thickness of 10 μm was formed on the outer peripheral surface of the endless belt after performing alkali etching treatment and cleaning in the same manner as in Example 1. Subsequently, a nickel layer having a thickness of 6 μm was formed thereon by electrolytic plating. Thereafter, a fluororesin dispersion paint (trade name: EN-710CL, manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) was applied onto the nickel layer, and baked in an oven at 380 ° C. for 1 hour. The thickness of the fluororesin layer was 30 μm.

The fixing belt thus prepared was mounted on the electromagnetic induction heating fixing device used in Example 1, and 200,000 sheets were passed through. When the power factor before the sheet passing test was 1.0, the fixing belt was passed through. The post paper power factor was 0.97, almost unchanged. In addition, the warm-up time before and after the passage was 11 seconds, and the temperature distribution after the passage remained uniform.
However, an offset phenomenon has occurred in which toner adheres to the surface of the fixing belt. This is because the rigidity of the entire fixing belt becomes too large, and the angle formed by the sheet peeling direction and the tangential direction of the belt circumference becomes small, and the releasability from the toner is lowered. Moreover, the color developability in a color image was also impaired. This is because the effect of wrapping the toner in the belt cannot be obtained sufficiently.

(Example 11)
A polyimide endless belt having a film thickness of 60 μm and an outer diameter of 30 mm was prepared using a polyimide resin (trade name: U Varnish-S, manufactured by Ube Industries) as a heat-resistant resin protective layer. Next, a copper layer having a thickness of 22 μm was formed on the outer peripheral surface of the endless belt after performing alkali etching treatment and cleaning in the same manner as in Example 1. Subsequently, a nickel layer having a thickness of 6 μm was formed thereon by electrolytic plating. Thereafter, a fluororesin dispersion paint (trade name: EN-710CL, manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) was applied onto the nickel layer, and baked in an oven at 380 ° C. for 1 hour. The thickness of the fluororesin layer was 30 μm.

The fixing belt thus prepared was mounted on the electromagnetic induction heating fixing device used in Example 1, and 200,000 sheets were passed through. When the power factor before the sheet passing test was 1.0, the fixing belt was passed through. The post paper power factor was 1.0, unchanged. In addition, the warm-up time before and after the passage was 11 seconds, and the temperature distribution after the passage remained uniform.
In the formation of a color image, an offset phenomenon in which toner adheres to the surface of the fixing belt has occurred. This is because the rigidity of the entire fixing belt becomes too large, and the angle formed by the sheet peeling direction and the tangential direction of the belt circumference becomes small, and the releasability from the toner is lowered. However, no offset occurred when forming a monochrome image. In addition, the color developability in the color image was somewhat impaired. This is because the effect of wrapping the toner in the belt cannot be obtained sufficiently.

(Example 12)
A polyimide endless belt having a film thickness of 60 μm and an outer diameter of 30 mm was prepared using a polyimide resin (trade name: U Varnish-S, manufactured by Ube Industries) as a heat-resistant resin protective layer. Next, a copper layer having a thickness of 10 μm was formed on the outer peripheral surface of the endless belt after performing alkali etching treatment and cleaning in the same manner as in Example 1. Subsequently, a nickel layer having a thickness of 12 μm was formed thereon by electrolytic plating. Thereafter, a fluororesin dispersion paint (trade name: EN-710CL, manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) was applied onto the nickel layer, and baked in an oven at 380 ° C. for 1 hour. The thickness of the fluororesin layer was 30 μm.

The fixing belt thus prepared was mounted on the electromagnetic induction heating fixing device used in Example 1, and 200,000 sheets were passed through. When the power factor before the sheet passing test was 1.0, the fixing belt was passed through. The post paper power factor was 0.97, almost unchanged. In addition, the warm-up time before and after passing through was 10 seconds, and the temperature distribution after passing through the paper remained uniform.
However, an offset phenomenon in which the toner adheres to the surface of the fixing belt has occurred to some extent. This is because the rigidity of the entire fixing belt becomes too large, and the angle formed by the sheet peeling direction and the tangential direction of the belt circumference becomes small, and the releasability from the toner is lowered. However, no offset occurred when forming a monochrome image. Moreover, the color developability in a color image was also impaired. This is because the effect of wrapping the toner in the belt cannot be obtained sufficiently.

(Comparative Example 3)
A polyimide endless belt having a film thickness of 60 μm and an outer diameter of 30 mm was prepared using a polyimide resin (trade name: U Varnish-S, manufactured by Ube Industries) as a heat-resistant resin protective layer. Next, the outer peripheral surface of the endless belt was subjected to alkali etching treatment and cleaning, and then subjected to electroless nickel plating treatment to form a nickel layer of 0.5 μm. Next, using this electroless nickel plating film as an electrode, a nickel layer having a thickness of 10 μm was formed thereon by electrolytic plating. Subsequently, a copper layer having a thickness of 5 μm was formed thereon by electrolytic plating. A fluororesin (PFA) dispersion paint (trade name: EN-710CL, manufactured by Mitsui DuPont Fluoro Chemical Co., Ltd.) was applied on the film, and then left in a 380 ° C. furnace purged with nitrogen for 1 hour to obtain a fluororesin film. The fixing belt was prepared by firing. The film thickness of the formed PFA layer was 30 μm.
Here, the specific resistance ρ of nickel is 6.84 × 10 ⁻⁶ Ω · cm, and the specific resistance ρ of copper is 1.67 × 10 ⁻⁶ Ω · cm.

  The fixing belt thus prepared was attached to the electromagnetic induction heating fixing device used in Example 1, and an attempt was made to perform a paper passing test. However, even if it took 30 seconds to reach a predetermined temperature (temperature for melting the toner), it did not reach. It was.

  Table 1 shows a summary of the evaluation results regarding the warm-up time, the temperature distribution in the fixing belt, and the power factor.

1 is a schematic cross-sectional view showing an example of an electromagnetic induction heating fixing device using a fixing belt of the present invention. FIG. 3 is a schematic cross-sectional view illustrating a configuration example of a fixing belt of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fixing belt 10a ... Heat-resistant resin protective layer 10b ... Metal heating layer 10c ... Metal protective layer 10d ... Elastic layer 10e ... Release layer 11 ... Pressure member 11a ... Base material 11b ... Elastic body layer 11c ... Release layer 12 ... Electromagnetic induction device 12a ... electromagnetic induction coil 13 ... pressing member 14 ... unfixed toner image 15 ... recording medium

Claims (4)

In a fixing belt that includes a metal heating layer that generates heat due to an eddy current generated when a magnetic field is applied, and is fixed by heating and pressing an unfixed toner image formed on the surface of the recording medium.
A protective layer made of a heat-resistant resin provided on the surface of the metal heating layer opposite to the recording medium; and a metal protection provided on the surface of the metal heating layer on the recording medium side. A fixing belt, wherein the metal heating layer and the metal protective layer satisfy the following formula (1):
・ Formula (1) ρ _A > ρ _B
[In the formula (1), ρ _A represents the specific resistance (Ω · cm) of the metal protective layer, and ρ _B represents the specific resistance (Ω · cm) of the metal heating layer. ] 2. The fixing belt according to claim 1, wherein a specific resistance ρ _A of the metal protective layer is twice or more a specific resistance ρ _B of the metal heating layer. A fixing belt including a metal heating layer that generates heat due to an eddy current generated when a magnetic field is applied; a pressing member that contacts the fixing belt to form a nip and rotates; and the pressing member of the fixing belt includes: In a fixing device including a pressing member that presses a surface opposite to the provided side, and an excitation coil that applies a magnetic field to the metal heating layer by flowing an alternating current,
The fixing device according to claim 1, wherein the fixing belt is the fixing belt according to claim 1. An image carrier, charging means for charging the surface of the image carrier, latent image forming means for forming a latent image on the charged surface of the image carrier, and developing the latent image with a developer to form an unfixed toner image An image forming apparatus comprising at least a developing unit that forms a toner image, a transfer unit that transfers the unfixed toner image to a transfer target, and a fixing unit that heat-fixes the unfixed toner image on a recording medium.
The image forming apparatus according to claim 3, wherein the fixing unit is the fixing device according to claim 3.

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